(a) Field of the Invention
The present invention relates to a new heatresistant composition particularly useful to produce heatresistant boards and tubes capable of resisting to high temperatures for substantial periods of time. The invention also relates to the boards and tubes obtained from such a composition by wet spinning.
(b) Brief Description of the Invention
U.S. Pat. application Ser. No. 246,198 filed on Nov. 8, 1988 in the name of the same Applicant, discloses and claims a fibrous-like synthetic forsterite product which is particularly useful as an insulating material. This product which is presently offered for sale under the trademark FRITMAG and will be called as such hereinafter, is obtained by subjecting chrysotile asbestos fibers of any commercial grade, having an MgO: SiO2 ratio lower than 1:1, to calcination at a temperature of from 650.degree. C. to 1450.degree. C.
FRITMAG has a raw loose density of from 3 to 40 pounds per cubic foot, a thermal conductivity K factor of from 0.25 to 0.40 BTU in/hr..degree. F.ft.sup.2 and a fusion point of about 1600.degree. C. to 1700.degree. C. It possesses a somewhat fibrous structure ressembling that of the chrysotile asbestos fibers from which it derives, although this fibrous structure has shown to disappear upon rough manipulation, when subjected to pressure, or when mixed with other material. Then, the fibrous structure is lost but the product has and always retains a high insulating value which is quite superior to granular forsterite or similar to KAOWOOL (trademark) or rockwool.
In the above-mentioned U.S. Pat. application, it is mentioned that FRITMAG may be used as a substitute for asbestos, whenever a fibrous material to be used in bulk and having high insulating qualities is needed. Indeed, FRITMAG is fibrous and has a loose density range substantially identical to asbestos. It also has high insulating properties and is devoided of all the undesirable health problems allegedly attributed to asbestos.
In the above-mentioned U.S. Pat. application, it is also suggested to mix FRITMAG with an inert filler and a binder in order to form an insulating composition adapted to be shooted onto any surface to be insulated or to be moulded in the form of slabs for roof insulation. However, no specific example of such a composition is given, except for a short reference made in the specification to a possible mixing with other materials, such as Portland cement. Similarly, no method of manufacturing slabs from such a composition is disclosed, although it is obvious that some of the methods presently used on an industrial scale to manufacture slabs may not be applicable if FRITMAG is part of the combination, because of the change of structure that has been noticed in this product when it is subjected to pressure or mixed with other materials.